The present invention relates to an address information reading-out apparatus of a fiber-distributed data interface (FDDI) system, and more particularly, to an address information reading-out apparatus for automatically converting 8-bit data into 16-bit data.
Generally speaking, an FDDI system is a high speed local network standard succeeding Ethernet (IEEE802.3) and a token ring network (IEEE802.5), for corresponding to the need of a high speed data transmission and is standardized by a task group (X3T9.5) of the American National Standard Institute. The FDDI system is a high speed (100Mbps) network and is being put to practical use under the interest of businesses and computer manufacturers.
FIG. 1 is a diagram for illustrating the concept of a conventional FDDI network. An FDDI station 1, an FDDI station 2 and an FDDI station 3 are connected to an Ethernet A, an Ethernet B and an Ethernet C, respectively. FDDI station 1 transmits data to FDDI station 2, FDDI station 2 transmits data to FDDI station 3 and FDDI station 3 transmits data to FDDI station 1, thereby forming a network. Thus, if Ethernet A wants to transmit data to Ethernet B, FDDI station 1 receives data from Ethernet A and transmits it to FDDI station 2. Then, FDDI station 2 recognizes the destination address of the received data. If the destination address is "B," FDDI station 2 transmits the data to Ethernet B. As above, if the destination address of data is recorgnized to be in a corresponding Ethernet by a given FDDI station, the station transmits the data to the corresponding Ethernet. This process is called a forwarding operation. (Here, if the detected destination address is not in the corresponding Ethernet, the forwarding operation is not performed.)
As described above, while the data generated from each FDDI station circulates a closed transmission loop via the FDDI stations, each of the FDDI stations receives the data produced by itself. Here, if the packet is made by an FDDI station itself, the packet must be removed to prevent an endless circulation within the network. As above, when the packet transmitted from an FDDI station returns to the FDDI station itself, the packet is to be removed by the FDDI station. This process is called a stripping operation.
FIG. 2 is a block diagram of a conventional FDDI station system. The FDDI station system relates to a packet filtering and a stripping logic construction. A packet received from a physical layer 40 of the FDDI network transmission cable is input to an FDDI controller 30 as 8-bit data. FDDI controller 30 converts the 8-bit data of the received packet into 32-bit data and writes it in a memory 20. Here, FDDI controller 30 transmits a control signal for indicating the termination of the packet reception to a central processing unit (CPU) 10. In order to determine whether the received packet is to be forwarded to another network, the CPU 10 performs a forwarding program, constructs a database, and searches the destination address of the packet.
However, when network traffic increases in a system which combines the FDDI network (having a data transmission rate of 100Mbps) and some other kind of network, such as Ethernet, the forwarding rate is dropped due to the excessive load on the system's CPU. That is, when the forwarding of the received packet is determined according to a processing program, the packet transmission rate between the networks is lowered, thereby deteriorating the performance of the system.